18-04-2014, 03:24 PM
COMMON COLLECTOR AMPLIFIER
AIM:
1. To measure the voltage gain of a CC amplifier
2. To draw the frequency response of the CC amplifier
APPRATUS:
Transistor BC 107
Regulated Power Supply (0-30V)
Function Generator
CRO
Resistors 33KΩ, 3.3KΩ, 330Ω, 1.5KΩ, 1KΩ, 2.2KΩ & 4.7KΩ
Capacitors 10µF-2Nos
100µF
Breadboard
Connecting wires
THEORY:
In common-collector amplifier the input is given at the base and the output is taken at the emitter. In this amplifier, there is no phase inversion between input and output. The input impedance of the CC amplifier is very high and output impedance is low. The voltage gain is less than unity. Here the collector is at ac ground and the capacitors used must have a negligible reactance at the frequency of operation.
This amplifier is used for impedance matching and as a buffer amplifier. This circuit is also known as emitter follower.
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. For calculating the voltage gain the input voltage of 20mV peak-to-peak and 1 KHz frequency is applied and output voltage is taken for various load resistors.
3. The readings are tabulated.
The voltage gain calculated by using the expression, Av=V0/Vi
4. For plotting the frequency response the input voltage is kept constant a
20mV peak-to- peak and the frequency is varied from 100Hzto 1MHz.
5. Note down the values of output voltage for each frequency.
All the readings are tabulated the voltage gain in dB is calculated by using the expression, Av=20log 10(V0/Vi)
6. A graph is drawn by taking frequency on X-axis and gain in dB on y-axis on Semi-log graph sheet.
The Bandwidth of the amplifier is calculated from the graph using the Expression, Bandwidth BW=f2-f1
Where f1 is lower cut-off frequency of CE amplifier
RESULT:
The voltage gain and frequency response of the CC amplifier are obtained. Also gain Bandwidth product is calculated.